Identification and expression analysis of the heat shock transcription factor (HSF) gene family in Populus trichocarpa

Abstract

Abstract In plants, heat shock transcription factors (HSFs) play key roles in regulating the heat shock (HS) response. Therefore, the genes encoding HSFs are important for adaptation to high temperatures and for tolerance to other abiotic stresses. There have been many studies on these genes in herbaceous plants, but few on the HSF family in woody plants. In this study, we identified 31 HSF genes in Populus trichocarpa and investigated their phylogenetic relationships with HSF genes in Arabidopsis and rice. Analyses of chromosomal duplications revealed that tandem/segmental duplications contributed to the expansion of the HSF gene family in P. trichocarpa. Gene structure was analyzed by investigating exon/intron organization and by using the MEME motif finder. Changes in gene expression were investigated using exPlot and digital northern analyses. Interestingly, nine of the HSF genes showed significant variations in expression patterns, suggesting that they have roles in stress responses. We evaluated changes in the transcript levels of the HSFs in response to abiotic stresses (heat, cadmium, salt, abscisic acid, and drought stresses) by analyzing log 2 fold change data. The transcript levels of the PoptrHSFA4a, PoptrHSFA4b and PoptrHSFA5a genes markedly increased in response to a wide range of stresses. The results of this study provide further information for cloning and expression of HSF genes, and for functional studies on the roles of these genes during development and in the responses to various environmental stimuli. Our results may help researchers design more efficient strategies to study the P. trichocarpa HSF family